Image loses quality/details when opened in ImageToolbox

[e-t-l]

Describe the bug

When opening an image in ImageToolbox, the preview of it is blurrier/lower quality than the original, even when no resizing, compression, or conversion has been applied. It's not just the in-app image preview, though; if the image is saved—even if no changes have been made to it—the new saved image is lower quality than the original, despite being the same pixel dimensions and the same size file as the original.

Steps to reproduce

1. Take a high resolution photo (e.g. 12MP)
2. Open it in a normal gallery app and zoom in to view some in-focus details
3. Open the same image in ImageToolbox
4. Using any mode (e.g. crop, single edit) zoom in on the same area of detail on the image
5. Observe that there is less detail/more blurriness in ImageToolbox
6. Without applying any edits, save the image
7. Open the saved image in a gallery app and compare it to the original image. Observe that both have the same pixel dimensions, but the newer saved image is noticeably lower quality details.

Expected behavior

ImageToolbox should be capable of editing and saving full-quality images.

Screenshots

No response

Device

Google Pixel 8 Pro

OS

Android 16

Locale

No response

App Version

3.4.0

FOSS or Market

Market (Google Play)

[T8RIN]

That's probably because of recompression. The image is stored not fully losslessly, because it's decoded to raw pixels, some operations are applied to them, and then all the pixels are compressed back into an image.

[e-t-l]

That makes sense, but it's a problem. Other photo editors manage to open photos without noticeably decreasing their quality. Opening + Saving a lossy image file once should not be enough to cause visible artifacts (especially if there haven't even been any operations applied!)

[T8RIN]

Because they maybe saving original image if no changes applied, i really don't know what i can do about this thing

[e-t-l]

Ok. Listen. Other photo editors also don't lose noticeable amounts of quality even when they do make an edit. That means that either...

1. ImageToolbox is using a buggy decompression algorithm when it initially loads an image into the editor, in which case the algorithm should be replaced,
   or
2. the algorithm is fine, but ImageToolbox's code is causing data loss somewhere else in the processing, in which case the buggy code should be fixed.

Those are the two main options for "what to do about this thing." Whereas, shrugging and dismissing concerns of bugs causing disproportionate data loss? That is not likely to encourage people to trust your apps.

[T8RIN]

Neither of them is true, try to use the nearest scale mode

[e-t-l]

Nearest scale model of what? Is this a setting in the app you want me to change?

[T8RIN]

yes, it's a setting when saving

[carlosame]

Ok. Listen.

I don't think that the tone of some of the replies is particularly helpful, but it is indeed true that when I zoom a preview of a JPEG image with Image Toolbox it isn't as sharp as when zoom-viewed through Gallery-type apps (although it appears brighter). Only happens when zooming (the whole image appears similar if not the exact same).

I checked with two different gallery apps, guess that both use the standard Android API to display and zoom the image. Maybe the Android API quietly performs some processing when zooming while the Toolbox doesn't?

Could post screen captures (P3 display) where the effect is obvious.

[T8RIN]

Image toolbox downsample images in preview mode

[kryoqa]

I'm unsure if this is related, but when applying a filter on Image Toolbox, the output image is blurry. I tried it with both PNG and JPG file formats, the result is blurrier/noticeable quality loss. I also tried with 'Explicit' and 'Flexible' resize type and 'Bilinear, Basic, Cubic, Lagrange' scale modes.

I'm not sure if I am doing something wrong, hence didn't want to create a separate issue.

When I applied the filter via another gallery app, the image had no blurriness/loss of quality.

[T8RIN]

If you want to apply filters or draw with minimal quality loss, you should use the dedicated tools inside the app instead of SingleEdit, which is more convenient but can introduce extra downsampling.

[T8RIN]

Applying filters in separate Filters tool instead of SingleEdit will provide full quality result, same for drawing etc